It is often desirable in a printing process involving a continuous stream of images laid down upon a moving paper web to incorporate other post-production processes to the web downstream of the printing process. These post-production processes may include, for example, page or job separation, hole punching, color logo application or folding operations. The problem with performing such post-production processes or operations is that the web transferred between the image and the post-production machines may not contain standard length pages or may otherwise have pages in locations upon the web that are difficult to gauge. Thus, the post-processing device must have some means for accurately locating each page presented to it, and furthermore, once each page location is found, must have a means of distinguishing between each individual page sent to it to determine which page must include a given post-production operation.
An additional problem with keeping track of processed pages as they are transferred to a post-production device is that the two devices may run at unsynchronized speeds, especially where they are discrete and separate units. As such, slack may develop in the transfer loop of web between the two devices, resulting in more images en route than expected and potential misapplication of the post-production operation.